Speaking-telephone



(No Model.)

J. H. ROBERTSON.

SPEAKING TELEPHONE. No. 289,309. Patented Nov. 27, 1883.

was...

"NITED STATES PATENT Fr es.

SPEAKING-TELEPHONE.

$PECIFICATION forming part of Letters Patent No. 289,309,

dated November 27, 1883.

Application filed February 10, 1883. (No model.)

To all whom it may concern Be it known that I, JAMES H. Bonna'rson, of the city of Brooklyn, in the county of Kings and State of New York, have invented a new and useful Improvement in the Receiving-Instrument of Speaking-Telephones, of which the following is a specification, reference being had to the accompanying drawing, forming part of the same, the drawing being a side view, partially in section, of a telephone containing my invention connected with transmitting devices.

My invention relates to atelephone-receiver in the secondary circuit of an induction-coil, in the primary circuit of which is the transmitter, the secondary circuitbeing so arranged that the induced current passes through vibrative electrodes, as well as the helix of the receiving electro-magnet, as herein described,

whereby the change produced in the primary current by the vibrations of the transmittingdiaphragm are accompanied by simultaneous changes in the secondary current produced by the corresponding vibrations of the receivingdiaphragm.

The lower portion of the figure in the drawing represents atelephone-transmitter consisting of the diaphragm A, the vibrating electrode B, the battery 0, the battery-wires a, constituting the primary circuit of an induction-coil, the helix D in said primary circuit, the core I), the secondary wires b b, and the helix E of the induction-coil wound upon the helix D of the primary wire. The wire I) is grounded in the usual way, and the wire 1) extends to the receiver and then to ground. (Not shown.) This is the most simple form of an ordinary contact-transmitter. If preferred, the transmitter described in Letters Patent No. 276,631, issued to me May 1, 1883, may be used.

The upper part of the figure represents my receiver, in which J is the diaphragm, mounted in a case or holder (not shown) in the usual way, and having secured to it a contact-piece or electrode, 6.

G is the core of an electro magnet, on which is wound the helix Fin the secondary circuit.

The said core is hollow, and into one end is fitted a screw-plug, H.

I is an armature connected to one end of a spiral spring, 0, that is placed in the hollow of said core G, the opposite end of the spring resting against the plug H. 011 the said armature is fixed the contactpoint or electrode (1, and the armature is thus arranged to vibrate freely, under the influence of the said magnet, in front of the pole or poles of the same and between the magnet and the dia phragm,with the described electrodes pointing toward each other. The spring 0 is to be so adjusted that said electrodes will be in contact. The course of the secondary circuit is, as shown, from the coil E of the secondary wire b, that is grounded by wire I), through wire Z2, coil F, wire b core G, plug H, spring a, armature I, electrodes at and e, diaphragm J, and wire I), to ground. The wire I) may, if preferred, be connected immediately to the electrode 6 on the diaphragm, as when a dia phragm is used formed of non-conducting material. The armature I must of course be made of soft iron or equivalent metal capable of magnetic induction. The electrodes d and e may be of steel, which material, I find, enables the receiver to reproduce most distinct- 1 y articulate sounds spoken at the transmitter; but steel is subject to the objection thatit will corrode at the point of contact between the electrodes. On this account platinum electrodes are preferable to steel, although the reproduction of articulate sounds with platinum electrodes is not quite so perfect as with steel electrodes.

By the use of electrodes, one or bot-h of carbon, in this connection, corrosion will be obviated; but I find that the articulation when carbon is employed is less distinct than with either platinum or steel. I find that by making the vibrative electrodes d and e a part of the secondary circuit, so that the induced current p asses through them, as described, thereproduction of artica late speech at the receiver is improved.

What I claim as my invention, and desireto secure by Letters Patent, is-

In a telephonereceiver, an clectro-magnet in the secondary circuit of an induction-coil, in the pri-1'nary circuit of which is the transmitter, the diaphragm provided with an elec- 5 trode, a vibrative armature provided with an electrode, and interposed between the magnet and diaphragm, with the electrodes in contact and forming part of the seconda.

ary circuit, so that the secondary current will pass'through said electrodes, allconstructed 10 and combined as and for the purpose de scribed.

JAMES H. ROBERTSON. Vitnesses:

A. G. N. VERMILYA, A. S. FITCH. 

